In the last entry, you saw those cool, circular tunnels that will house Manhattan's new 7 Train extension, lined with pre-fab concrete sections. Above is a photo of a similar tunnel in Delhi. Question is, how did they dig and line these things?
They use what are called TBMs, or Tunnel Boring Machines. These massive machines are essentially moving factories that cut through the rock, excavate the waste out of the back, and install the concrete shielding, all while pushing itself along like an inchworm. You'll understand the process better after viewing the video at the bottom of this entry, but first, here's some examples of what TBMs look like from the front:
I think this one has no motor and is powered by the really strong guys in the red and
orange shirts. (The guys in green and yellow shirts are there to yell encouragement.)
Japan has a bad-ass triple tunnel boring machine.
In a manner of speaking, it's three times as boring.
The 7 Train job is being undertaken by an international conglomerate called S3 Tunnel Constructors, and the TBMs they're using lack the cool paint jobs of the models above:
S3 is also doing NYC's ongoing 2nd Avenue subway line. But unlike the 7 Train crew, the 2nd Avenue guys have machines with fun, yellow paint jobs.
The back ends of the machine are not so pretty.
The S3 tunneling crews have been working beneath Manhattan 24 hours a day, 5 days a week to bore the tunnels. As you can imagine it is dull and tedious work. The most exciting part is the "breakthrough" moment, when at long last they crack through that final wall and into the open space at the other end. As per tradition, elated construction workers jump up and down, clap their hands and pass out exotic, fruity cakes.
Orange Vest: "You guys are jerks. I told you a million times I'm allergic to lingonberries."
There are a bunch of YouTube videos showing TBMs in action, but sadly, the one that does the best job also has the lowest resolution and crappiest sound. Still, it will help you see why these things are essentially "moving factories:"